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Patented August i2, i873.

UNITED. STATES PATENT OFFICE.

THOMAS A. EDISON, OF NEWARK, NEW JERSEY, ASSIGNOR TO HIMSELF i ANDGEORGE HARRINGTON, OF WASHINGTON, D. C.

IMPROVEMENT IN CIRCUITS FOR AUTOMATIC TELEGRAPHS.

Specification forming part of Letters Patent No. 141,773, dated August12, 1873 application lcd January 15, 1873.

To all whom it may concern:

Be it known that I,` THOMAS A. EDISON, of Newark, in the county of Essexand State of New Jersey, have invented Improvements in Circuits forChemical Telegraphs, of which the following is a specification:

YThis invention is intended for rendering the reception of the messagemore reliable and free from blurring or tailings upon the chemicalpaper. The line is kept statically charged by a battery, the circuit ofwhich is interrupted with immense rapidity by an electromagnetic engineor other device. At the receiving end there is a shunt with anelectromagnet in it. The electric tension is adjusted by a rheostat atthe transmitting-station, so

' that ordinarily there will not be any mark at -the receiving-stationin consequence of the electro-magnet and shunt; but when the tension inthe line is increased by the current going through the perforations ofthe paper at the transmitter and directly to the line, so as to cut outthe rheostat, then a mark is made at the receivinginstrument, but therewill not be any attenuation of the pulsation to nro- `duce tailings.

At the receivingstation I employ two or more styluses or pens, allconnected with the main line, and to each is a shunt-circuit and anelectromagnet. The magnets are of varying character or power; hence theywill act differently upon the stylus, and one will be sure to make alegible mark, although the electric conditions may vary from time totime or during the reception of the message, and the operator will beable to read the mcssage reliably upon one of the twoor morecorresponding lines of marks on the strip before him.

In the diagram I have illustrated my improvement.

`The battery a, rheostat b, and rapid contactbreakerc are iu the mainline orv circuit. The rheostat, which may be adjustable, only allows theimmensely rapid pulsations from c to pass sufticiently upon the line tokeep the same statically charged to the required extent. Thetransmitting-instrument d is in a .shunt that connects with the line onboth sides of the rheostat; hence the pulsations through the paper reachthe line ,direct and increase the electric tension suticiently tooperate the receiving-instrument. The receiving-instrument h may be ofany suitable character; but I nd that there should be either anelectro-magnet in a shunt-circuit to neutralize the static electricityby the countercurrent as the magnet discharges, or else a battery andrheostat with the polarity of the shunt or local circuit the reverse ofthatof the main line. I, however, prefer to luse two or more styluses orpensait, connected to the main line and to shunt-circuits, in which areplaced. the electro-magnets k k.

The tailings from the pulsations are neu tralized by the reversecurrents set up in the shunt-circuits as the electro-magnets dischargethemselves; and by employing magnets of diiierent powers or qualitiesthere will be greater certainty of the record being clear and legible inone of the two or more lines oi' marks upon the strip of chemicalpaper,be cause the coils of the magnets are of different resisting powerto vary the currents passing to the paper; and the secondary currentinduced in the magnet is more or less active as it is discharged.

y Where a drop copy is desired it may be obtained upon the line byplacing the two ends of the wires in a glass of water, on, and also thetwo poles of a local circuit, in which is a chemical-receivinginstrument, t. By adjustl ing the proximity of the ends ofthe main-linewires to those of thelocal circuit the necessary division will be madefor producing the record without materially interfering with the mainline. At intermediate stations a branch connection, o, may be made tothe earth with a resistancecoil, r, therein, and one or more of thesecoils may be brought into action by a switch, and these coils may fermparts of eleetromagnets, or a separate electro-magnet, s, be introduced,and a drop copy may be taken in a shunt-circuit, t, in this branchearth-circuit, by the electro-magnet acting upon a circuit-closinglever.

The magnet s may be made to operate arelay or sounder or areceiving-instrument at the local station, indicated at u.

I am aware that'liquid rheostats or resistances have been made useof;but I am not aware that the ends of the line and of a shuntcircuit havebeen 4introduced in a liquid, and the four ends so varied or adjusted inposition as to proportion the shunt and main-line currents.

I claim as my inventionl. The resistance b and transniitting-instrumentd, arranged in connection with the line, the battery a, and the rapidcircuit-breaker c, as and for the purposes set forth.

2. Two or more styluses or pens connected with the main line and withshunt-circuits, in which are diering magnets for operation upon thechemical-receiving paper, as set forth.

3. The vessel of liquid receiving the two ends of the shunt-circuit andthe two ends of the main line to vary the strength of theshuntcircuitaccording to lthe relative positions of such circuit ends,as set forth.

Signed by me this 12th day of December, A. D. 1872.

THOIWIAS A. EDISON.

Witnesses:

GEO. T. PINCKNEY, GHAS. H. SMITH.

